The present invention relates generally to imaging systems, and more particularly, to a Radon transform based method for target azimuth aspect estimation for use with imaging systems and a target acquisition system using the method.
In prior art radar systems and signal processing methods used therewith, target azimuth aspect estimations place a target-sized rectangular template on an image and then slide and rotate the template until the energy within the template is maximized. For example, an approach developed at Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL) operates in such a manner. This is disclosed in a paper by L. Novak et al. entitled "Performance of a high-resolution polarimetric SAR automatic target recognition system," Lincoln Laboratory Journal, vol. 6, no. 1, pp. 11-24, Spring 1993.
As with the MIT/LL discriminator, the Army Research Laboratory (ARL) false alarm mitigation stage also uses a binary correlation algorithm. The algorithm uses two series of masks. This is disclosed in a paper by G. Stolovy et al. entitled "An overview of the ARL end to end software based synthetic aperture radar automatic target recognition workstation," presented at the Sensors and Electron Devices Symposium, U.S. Army Research Laboratory, January 1997. In this technique, a bright mask corresponds to the brightness areas in the target and a surrounding mask corresponds to dark areas or clutter surrounding the target. Each template has associated offset and threshold parameters. The shape of the template change considerably with target azimuth. Forty templates are used to span a full 360 degrees in azimuth.
There are problems with these two methods. A major problem is that these estimations are computationally intensive. For M targets, they require M different templates. The M templates are translated and rotated to cover the entire image over a full 360 degrees. Another problem is that the estimation performance is degraded if the target size is not provided.
Accordingly, it is an objective of the present invention to provide for an improved method for target azimuth aspect estimation for use with imaging systems such as synthetic aperture radar, forward looking infrared, and laser radar systems, and the like, and a target acquisition system using the improved method.